At noon, a train leaves New York for Toronto while another leaves Toronto for New York. It takes one train hours and the other hours to make the trip. If both maintain constant speeds and travel along parallel tracks, at what time do they pass each other?Source: NCTM Mathematics Teacher, October 2006

SolutionWe use the following variables = time (duration) in hours when the trains pass each other = New York – Toronto distance in miles = distance in miles from Toronto to the passing point = distance in miles from New York to the passing point
We calculate speeds and distances speed of slower train speed of faster train
Divide both sides by d = hours minutes

Answer: p.m.

Alternative solution 1Suppose train 1 is slower than train 2. Since distance is proportional to time is to as is to hours